Progressive-burning smokeless powder



Patented Nov. 7, 1939 UNlTED STATES PROGRESSIVE-BURNING SMOKELESS POWDER Elton B. Allison, Kenvil, N. J., assignor to Hercules Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application October e, 1938,

Serial No. 233,591

3 Claims.

This invention relates to smokeless powder, and particularly to coated, deterred, or progressiveburning smokeless powder.

Smokeless powder, on combustion in the cham- 5 her of the min which it is used, tends to burn initially at a more rapid rate than is desired and thus produces-high breech pressures. This defeet is not overcome by using larger grains of powder, in the case of those powders intendedto give maximum ,results in center-fire rifle cartridges. Many attempts have been madein the past to deter the initial rate of burning of the powder grains by coating said grains with an agent, explosive or non-explosive, which will slow down the initial rate of combustion of the powder grains. thus extending the period of time taken by the grains to burn.completely, and in this way reduce the otherwise high breech pressure in the gun. 'I'h coating material used penetrates the powder grains more or less, so

- that, as the powder grains burn, the successively exposed surfaces contain gradually, less and less of the deterrent material, thus causing subsequent combustion of the powder grain to pro-.

ceed with increasing speed as the bullet travels down the bore of the gun.

In the past, many substances have been used, without complete success, to coat smokeless powder grains, e. g., suchmaterials as di- I ethyldiphenylurea, dimenthyldiph'enylurea, dinitrotoluene, alkyl phthalates, or mixtures thereof,

and various methods of applying such deterrent substances have been known.

The known methods of deterring or coating smokeless powders have not been completely effective in that they have not produced smokeless powders or high gravimetric density combined with high ballistic stability. By ballistic stability is meant the maintenance, with age, of the initial 0 ballstics produced by-the powder. For example,

- many or the coating agents continue to penetrate into the powder grain, particularly in warm cli-f thus alter their deterrent charac-.

mates; and teristics.

With modern loads 0': deterred smokeless powder it is, usual to flnd that the maximum velocity which can beobtained with a given projectile is limited,- not'by themaximum allowable pressure produced in the chamber of the sun. but by the powder capacity or the cartridge. However, an increase in the gravimetric density oi the powder would permit the use of greater powder charges and result in'an increased velocity or projectile.

It is the object of this invention to-produce tion in a barrel at a temperature within the range a coated smokeless powder which is baliistically stable with age and of high gravimetric (or loading) density. The high gravimetric density of my coated powders enables me to use greater charges than hitherto permitted by the volu- 5 metric capacity of the cartridge, which is a distinct improvement over prior art powders and an advantage which has been sought for many years by the art. My improved smokeless powder is not subject to clustering or sticking 1( together of the grains.

In the preparation of coated smokeless powder in accordance with my invention I use coumarin as the coating agent. This compound may be used alone or in combination with other coating 15 agents.

I may use as the powder grains to be coated either a single base (nitrocellulose) powder or a double base (nitrocellulose-nitroglycerine) powder. Although the powder grain may be of 241 any size Ihave found that my coating agent offers the most advantage when used with the larger caliber powders.

.=I'n practicing my invention, coumarin is applied to the smokeless powder as a solution there- 25 of in a volatile solvent which is substantially a non-solvent tor the smokeless powder. Among the volatile solvents which I have used are toluene, ethylene dichloride, petroleum naphtha, isopropyl alcohol, water, and ethyl alcohol, and 30 of these I prefer using by volume ethyl alcohol.

To parts by weight of smokeless powder I add from about 1 to about 10 parts by weight of coumarin dissolved in a suitable quantity of 35 solvent. 'I'he'smokeless powder is treated with coumarin in any suitable manner .for example by tumbling thepowder and the coumarin soluof from about 10 0. m about 95 0. for a period of timev between about 5 minutes to about 4 hours, after which the powder so coated may be subjected to further heat treatment to eliminate any remaining solvent, if this appears desirable. The 45 time and temperature of treatment as well as the quantity of coating will necessarily be varied withthe size of the powder grain employed, the type of firearm in which the powder is to be used, etc.

In the case of application of extremely heavy 50 I coatings to the .powder, when using a volatile solvent other than water, water may be added to the coated powder grains before elimination of the vola e solvent in order to prevent sticking and cl oi-the v 5 As specific illustrations of the carrying out of my invention, the following examplesdare given:

Example 1 Nine hundred and seven parts by weight of a :iouble base smokeless powder containing 20% nitroglycerine pressed through a 0.045 inch die having a 0.015 inch pin, and the strand so proiuced cut into 11 particles per inch was placed in a. sweetie barrelmaintained at 75 C. and to this Example 2 As a comparison with the above example I :oated 907 parts by weight of the same smokeless aowder as above in the same manner indicated Jefore with 45.3 parts by weight of symmetrical iiethyldiphenylurea (Centralite #1). A yield of 38% of unclustered powder was obtained having 1. low and unsatisfactory gravimetric density of ).919.

The powders prepared in accordance with ;he two examples above were fired in a .30 :aliber-1906 cartridge case 'using a 110 grain Juliet, the cartridge being loaded in each case with sufilcient powder to fill said cartridge to the Jase of the bullet. The results obtainedare ;hown in the following table:

Charge Mean velocity Powder from in over i153 foot Mean We grams range I FL/nc. Lba/q. huh example 1 62. 5 3, 435 60, G1) Example 2. 61.1 2,880 26,000

It m be noted in the above table that a powder coated with coumarin as disclosed by the present invention has an appreciable velocity increase over comparator Example 2 in which a prior art coating material is used. Furthermore, in comparison with Example 2 it will be noted that a greater charge of powder can be utilized in the same space in the cartridge in the case of Example 1, which is, of course, due to the higher gravimetric density of the powder prepared in accordance with this invention.

To illustrate the improvement in stability obtained by my coated powder, I- subjected it to Y warm storage using for comparison. a powder coated in the same manner with butylphthalyl butylglycollate. The results of this test are shown in the following table: 7

The marked improvement in ballistic stability is apparent from the above table. It will be understood that the foregoing are by way of iilustration only and that the scope of my invention is not to be limited thereto, except as hereinafter defined by the claims. e

What I'claim and desire to protect by Letters Patent is:

1. Smokeless powder grains surface coated with coumarin.

2. Double base smokeless powder grains surface coated with coumarin.

3. Smokeless powder grains surface coated with coumarinin amount from about 1% to about 10% by weight of the powder.

ELTON R. ALLISON. 

